JPH0244157B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for selectively forming a plating layer on a conductor on a printed circuit board, and in particular, a method for forming a selective plating layer on a conductor on a printed circuit board. The present invention relates to a method for partially forming a plating layer on a conductor on a substrate by partially forming a plating layer by electrolytic plating.

Conventional structure and its problems The conductor provided on the printed circuit board (printed wiring board and thick film printed circuit board are also referred to interchangeably) has anti-rust,
In order to highly achieve the purpose of improving electrical contact or soldering, forming a localized plating layer has often been used in the past. A plating method using an electrolytic process, that is, an electroplating method is suitable for forming a local plating layer on such a conductor. In this case, the conductors arranged on the printed circuit board are separated from each other and are in a so-called non-conducting state, so it is necessary to commonly connect each conductor to the cathode electrode body of the electrolytic system. Connection with the electrode body requires sufficient electrical contact as well as liquid resistance and ease of work.

OBJECTS OF THE INVENTION The present invention provides a method for forming a plating layer that facilitates connection between a base and a cathode electrode body and has good workability when forming a partial plating layer on a conductor on a printed circuit board.

Composition of the Invention The present invention summarizes the steps of exposing a part of a conductor in an annular area on a substrate, bringing a conductive ring into contact with the exposed conductor, and electrolytically plating the part of the conductor. According to this method, good electrical contact is made with conductors separated on the substrate, and partial plating can be easily and reliably formed using electrolytic plating. It is possible to form a plating layer.

DESCRIPTION OF EMBODIMENTS FIG. 1 shows the main parts of a printed wiring board used in an embodiment of the present invention, FIG. 1A is a plan view, and FIG. 1B is a sectional view taken along line a-a'. In this example, a conductor group 2 is provided on an insulating substrate 1 in a predetermined wiring shape.
Now, a method of selectively forming a plating layer on a portion where one end of the conductor group 2 is concentrated, that is, the portion of each conductor end 2-a, 2-b, 2-c, and 2-d will be described.

2A and 2B show that the conductor 2 of the insulating substrate 1 corresponding to FIGS. 1A and 1B is provided with a resin layer 3 that exposes a part and covers the other part, and FIG. 2 is a plan view showing a state in which a conductive ring 5 is brought into contact with an annular region 4 of the exposed conductor group, and a cross-sectional view taken along the line a-a'. The conductive ring 5 exposes the front surface of the substrate 1 within the annular region 4 and is pressed into conductive contact with the conductor group 2 existing on the exposed surface. Then, by placing these in an electrolytic plating bath and proceeding with the electrolytic plating process using the conductive ring 5 as a cathode, a predetermined plating layer 6 is obtained on each surface of the conductor group 2.

3A and 3B show the conductive ring 5 and the conductor end 2.
-a only is arranged in the inner ring part, and the other conductor ends 2-b, 2-
FIG. 3 is a plan view of a state in which the outer ring portion is brought into contact with c and 2-d, and a cross-sectional view thereof taken along the line a-a'. In this way, it is possible to make the properties of the attached plating layer different on the outside and outside of the ring, and usually it is thicker on the conductor end 2-a of the inner ring part, and thicker on the conductor ends 2-b, 2-c of the outer ring part. , 2-d, a thin plated layer with different grain quality is obtained. This fact is due to the difference in current density between the inside and outside of the conductive ring 5. This method can be used, for example, when the conductor end 2-a is used as the solid-state circuit element bonding part and the conductor ends 2-b, 2-c, and 2-d are used as the thin metal wire connection parts. It has the advantage that when you want to make adjustments, you can finish them all at once.

FIG. 4 is a perspective view schematically showing the contact relationship between the conductor group 2 and the conductive ring 5 that are held during the electrolytic plating process, and the conductive ring 5 is on the negative electrode (cathode) side of the electrolytic system. The conductor group 2 is electrically connected to the conductor group 2 within the annular region 4 thereof.

FIG. 5 is a cross-sectional view schematically showing a large number of conductive rings 5 mounted on an insulating substrate 1 and connected to a common cathode. The aim is to increase production efficiency.

FIG. 6 is a cross-sectional view of the conductive ring 5 held by the plate-like support 8 via the conductive silicone rubber 7, which allows the conductive ring 5 and the conductor group 2 to be connected to each other. Electrical contact is further improved and the plating process is stabilized. In this case, the conductive rubber 7 and the plate-shaped support 8 must also be provided with holes 9 through which the plating solution can penetrate.

In the embodiment of the present invention, an aluminum plate (1.0 mm thick) insulated with a resin layer is used as the insulating substrate 1, and the conductor group 2 is formed by etching a copper foil laminated layer with a thickness of approximately 70 μm. A wiring body is used. The plating layer 6 is made of gold, silver, or nickel and has a thickness of 1 to 5 μm. Furthermore, for the insulating resin layer 3, for example, an epoxy resin containing an aromatic amine curing agent is suitable, and the thickness is about 15 μm.
It is coated to a thickness of 300℃ and cured at 130℃ to 150℃ for about 30 minutes, resulting in no pinholes, moderate flexibility, and excellent resistance to alkaline plating solutions. It is sufficiently durable even for permanent use. The conductive ring 5 may be made of copper or stainless steel and brought into direct contact with the conductor group 2, or an elastic body such as conductive silicone rubber may be used as an intervening material.
Note that when using conductive rubber, it is advantageous in terms of liquid resistance to embed the cathode electrode body inside.

Embodiments of the present invention are applicable not only to a single solid printed circuit board, but also to forming a plating layer on a group of conductors on a film surface used in, for example, film carrier mounting technology. Sufficiently applicable.

Effects of the Invention As described in detail in the above embodiments, according to the present invention, formation of a partial plating layer on a conductor on a printed circuit board can be achieved with good workability. In particular, since the conductor group is brought into contact with the conductive ring, the current distribution during the electrolytic process is stabilized, and the uniformity or controllability of the plating layer is improved. Also,
By bringing the conductive ring into contact with the conductor group so that the conductor ends are exposed to the inner ring part and the outer ring part, and proceeding with the electrolytic plating process, the plating layer attached to each conductor end can be formed. The properties can be made different between the inside and outside of the ring, and the plating layer can be formed thicker on the inner ring and thinner on the outer ring.

[Brief explanation of drawings]

FIG. 1A is a plan view of the main part of the printed circuit board used in the embodiment of the present invention, FIG.
3 is a plan view of the main part showing the state in the electrolytic plating process, FIG. FIG. 4 is a schematic perspective view showing the process of implementing the present invention, and FIGS. 5 and 6 are cross-sectional views showing the steps of each embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Conductor group, 3... Insulating resin layer, 4... Annular region, 5... Conductive ring, 6...
Plating layer, 7... Conductive silicone rubber, 8... Plate support, 9... Hole.

Claims (1)

[Claims] 1. A conductor extended over almost the entire area of the board is partially exposed only on a predetermined inner surface of the board, and a conductive ring is placed in contact with the conductor within the predetermined inner surface, A method for forming partial plating on a conductor on a substrate, comprising a step of electrolytically plating a part of the conductor.